This invention relates to a cable assembly and, more particularity, to a cable assembly for connecting an amplifier to a loudspeaker in a sound reproduction system.
Within the chain of components comprising a typical professional or home audio system intended for the high-quality reproduction of music, the loudspeaker has evolved as the weakest link. Unlike other system components, loudspeakers are seldom designed to accurately reproduce complex musical waveforms or their laboratory equivalents such as pulses and square-waves. Nor is concern usually given to the modulus of input impedance versus frequency.
Many popular loudspeaker designs exhibit variations in impedance that range from a minimum of less than one ohm to a maximum exceeding 30 ohms. These variations in loudspeaker impedance are usually accompanied by a large reactive component which may shift from inductive to capacitive with only a small percentage shift in frequency.
Such large excursions in resistance and reactance seriously complicate the process of transferring power from the amplifier to the loudspeaker via a cable while insuring an optimum modulus in radiated sound pressure level (SPL) versus frequency. It appears that most audio cable designers have assumed that, due to the typical short length of loudspeaker cables (relative to the length of a "wavelength" at frequencies within the audio spectrum), the impedance of the cable, especially when compared to the impedance of the loudspeaker, is unimportant. In fact, the majority of presently available loudspeaker cables exhibit characteristic impedances that range from about 50 ohms to over 150 ohms, which is far greater than the impedance of a great majority of loudspeakers which averages about 8 ohms. This induces reflections because of the impedance mismatch between the cable and the loudspeaker (load), which causes ringing and/or audible distortions. This is similar to the "ringing" and blurring of the video image which results from a mismatch between the impedance of the R.F. cable (twin lead or coaxial transmission-line) and the input impedance of the television receiver.
Many prior art cables also suffer from "skin-effect" losses which add signal attenuation at higher audio frequencies which can degrade the perception of "definition" on short-duration musical transients. Other poorly designed cables exhibit the property of time/frequency dispersiveness due to the use of unsuitable dielectric material that causes different frequencies to travel along the cable at different velocities, resulting in the blurring or smearing of musical transients.